(57) A helically coiled wire insert (10) of the type used for tapped holes in parent material
that is generally softer than the bolt being screwed into the tapped hole, whereby
the two free end coils have a hook recess (14) on the inner screw thread of each and
the terminal end of each free end coil has a reduced transverse cross section along
one longitudinal axis of the wire. The surfaces (28, 29) of the hook recess (14) are
angled from the longitudinal axis of the insert to provide increased forces along
the longitudinal axis of the insert.
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